Shoe last inserts



May 7, 1963 w. P. FIELD SHOE LAST INSERTS 2 Sheets-Sheet 1 Filed Nov. 2,1 960 May 7, 1963 w. P. FIELD 3,088,147

SHOE LAST INSERTS Filed Nov. 2, 1960 2 Sheets-Sheet 2 United StatesPatent 3,988,147 SHOE LAST HJSERTS Walter P. Field, 157 Belmont St,Brochton, Rdass. Filed Nov. 2, 196:), Ser. No. 66,725 1 Claim. (ill. 12liil) This invention relates to shoe lasts, and more particularly toinserts or plugs for use therewith.

In the manufacture of shoes, one of the first operations ordinarily isto tack an insole to the bottom of the last. In the case of wood-bottomlasts such tacks may be driven directly into the wood of the last, butthe resulting nail holes tend to cause early deterioration of the last.Accordingly it is desirable to provide replaceable inserts at suchplaces of tacking in order to increase the life of the last.

In the case of metal-bottomed lasts it is of course necessary to provideinserts at the places of tacking because such metal bottoms, usuallysteel, are impervious to tacks.

Generally speaking shoe last inserts previously employed have beenexpensive, difi'icult to apply or replace, have required too frequentreplacement, or have not fit adequately, namely flush with the adjacentsurface of the last.

To illustrate the matter of fit, if the top of an insert is lower thanthe adjacent surface of the last, during the processing of the shoe inits manufacture a raised portion will appear in the insoleco-rersponding to a depressed surface of an insert. Likewise if thesurface of an insert rises above the adjacent surface of the last, adepressed portion will appear in the insole of the resulting shoe.

To illustrate further the matter of poor fit, if the surf-ace of aninsert is initially higher than the adjacent surface of the last, andscouring is required to remove the excess material from the insert, suchscouring not only involves substantial labor cost but such operationremoves anticorrosion material ordinarily applied to metal employed forlast bottoms.

By the present invention, there are provided shoe last inserts whichobviate difficulties of the prior art indicated above and additionallyprovide advantages hitherto not available. Shoe last inserts of thisinvention will be described below, and illustrated in connection with aspecific embodiment thereof in the drawings wherein:

FIGURE 1 is a bottom view of a metal bottomed last;

FIG. 2 is a fragmentary sectional view of a last showing afrusto-conical insert of this invention partially inserted in a lastcavity;

FIG. 3 is a view similar to FIG. 2 showing the insert completelyinserted in the last cavity;

FIG. 4 is an elevation of an insert of this invention;

FIG. 5 is a bottom plan view of the insert shown in FIG. 4;

FIG. 6 is a fragmentary bottom view of a last with an insert of elongatecross-section;

FIG. 7 is an elevation of the elongate insert shown in FIG. 6;

FIG. 8 is a bottom plan of the insert shown in FIGS. 6 and 7;

FIG. 9 is a vertical section taken on line 99 of FIG. 7;

FIG. 10 is a side elevation of a last showing inserts applied to sideportions of the last; and

FIG. 11 is a rear elevation of a last showing an insert applied to therearward portion of the last.

In FIG. 1 is shown a last 16 to the bottom of which is secured a metalplate 12 by means of fasteners 14. Last inserts 16 are shown in place,disposed at places where it is common to drive tacks to hold an insolein place during shoe making operations.

Ice

The shoe last insert of this invention is composed of chemically inertplastic material, specifically polyethylene. It is contoured and for-medto predetermined precise shape and dimension, conveniently by injectionmolding. As presently preferred the insert is of frustum shape with thelarger end of slightly greater cross-sectional dimension than the lastcavity to which it is to be applied and with the smaller end of slightlysmaller cross-sectional dimension than the shoe last cavity. In onepreferred form of the invention, the insert is of frusto-conical shapeand circular cross-section. For certain applications, the insert mayhave a cross-section of elongate character, conveniently with twoparallel sides joined by semi-circular arcs. For convenience ofinsertion the smaller end of the insert is marginally rounded. Asillustrated herein, the smaller end of the insert is depressed to formin effect an air trap and the insert is provided with a shallow grooveextending from the larger end of the insert along the inclined sidethereof and around the smaller end to communicate with said depressedportion. Such groove provides an :air vent, to permit adequate andpermanent seating of the insert in desired position.

Referring again to the drawings, particularly FIGS. 4 and 5, insert 16is of frusto-conical shape with the larger end 18 having a slightlygreater diameter than the smaller end 29. The marginal edges 22 of thesmaller end 20 are rounded. The central portion of the smaller end 20 isdepressed to form the air trap 24. A shallow groove 26 is shown asextending from the larger end 18 along the side of the insert to thesmaller end 2! and along and across said smaller end to communicate withsaid depressed portion 24. As illustrated the insert 16 is ofinjection-molded polyethylene.

As illustrated in FIGS. 2 and 3, last 12 is provided with a drilledcavity 23 of precise diameter and depth. In FIG. 2 insert 16 is shown aspartially inserted into the cavity 28 which may be done by hand withgreat ease due to the shape and precise dimensions of the insert. InFIG. 3 the insert 16 is shown as driven to the bottom of the cavity 23with the larger end of the insert flush with the adjacent surface of thelast.

So far as illustrative relative dimensions are concerned, and referringto FIGS. 2 and 3, if the cavity 28 is drilled to a precise diameter of/2", the larger outer diameter of the insert may be 0.515 and thesmaller outer diameter of the insert may be 0.495". The verticaldimension of the insert may be made to corerspond to the depth of thelast cavity.

The groove 26 performs a highly important and indeed essential functionin this invention in permitting the escape of air from the last cavityduring the incorporation of the insert therein. Due to the resilientnature of the polyethylene and the precise relative dimensions of theinsert and the last cavity, the polyethylene tends to flow and close thegroove 26 during the insertion operation and this flow tends to takeplace to the extent that the polyethylene of the insert fills the cavity12 snugly throughout its depth. The depressed portion 24 accommodatesany additional air at the bottom of the cavity and prevents unduepressure such as might cause the insert otherwise to rise.

Due to the precision character of the insert 16 the larger or upper endthereof lies flush with the adjacent portions of the last and hencerequires no scouring in the ordinary situation.

This feature saves labor and time and precludes the removal of anyrust-proofing surface from the metal portion of the last. In the eventhowever, that .a last cavity should be of insufficient depth, materialof the insert extending above adjacent portions of the last may beremoved in any suitable manner.

It Will be noted that when a contoured insert of this invention isdriven into a corresponding hole or cavity of the last, any air withinthe cavity and below the insert is released by means of the air vent orgroove. Thus there is prevented any buildup of air pressure beneath theinsert which would tend to dislocate the insert from its predeterminedposition. At the same time, the compressive effect of the walls of thecavity radially inwardly of the upper portion of the insert tends toclose tack holes when insole-holding tacks have been withdrawn.

The inserts of this invention may be of cross sections other than thecircular cross section specifically illustrated herein. Thus forexample, the cross sectional shape may be of generally long ovalcharacter, in which case the last cavity will be made of correspondingshape. Other shapes and modifications are within the purview of theinvention.

The elongate form of frusto-conical insert illustrated in FIGS. 6 to 11provides an extended area for the reception of insole tacks. Thismodification finds highly useful application in the .toe portions oflasts for pointed-toe shoes. Insert 30 is of frustum shape and itslarger end 32 has a slightly greater area than the smaller end 34.Insert 30 in cross-section is of elongate character with the twoparallel sides 36 and 38 joined by semi-circular arcs 49. The marginaledges 42 of the smaller end 34 are rounded. The central portion of thesmaller end 34 is shown as depressed to form the air trap '44. A shallowgroove or flute 46 extends from the larger end 32 of the insert down thelateral side 47 thereof and along the smaller end 34 thereof tocommunicate with depressed portion 44. In FIG. 6, insert 30 is shown inplace in pointed-toe last 48. The cross-sectional shape of insert 30 isadvantageous because of the relative ease with which a correspondinginsert-receiving cavity may be formed in the last.

In FIG. 10, inserts 16 and 30 are shown as incorporated in side portionsof last 10, illustrating the possibilities of 4 applying inserts of thisinvention to any portion of a last which may be damaged and requirerepair. V

In FIG. 11, an insert is shown as incorporated in the heel end of a last19, where tacks are frequently driven to assist in holding a shoe upperin place.

The slight flowing tendency of polyethylene tends furthermore to closeup to some extent tack holes left upon removal of tacks and thusincreases the life of the inserts.

The chemical inertness of polyethylene means additionally that there isno swelling thereof upon the lacquering of the completed last whichordinarily takes places after the incorporation of the inserts. Anyswelling characteristic otherwise would tend to cause the insert to riseabove the level of the adjacent surface of the last after suchlacquering operation.

It will he understood that the last inserts of this invention may beapplied to any desired portion of a last for repair or other purposes.

Having disclosed my invention, what I claim as new and desire to secureby Letters Patent of the United States is:

A pressure-formed polyethylene fi usto' conical plug for insertion intoa recess in a shoe last comprising polyethylene polymerized to such astate that the material is plastic and slightly resilient to receivetacks and tend to close the tack holes when the tacks are removed.

References Cited in the file of this patent UNITED STATES PATENTS Wellso. May 1, 1883

